Methods for retarding coke formation during pyrolytic hydrocarbon processing

Abstract

Methods are disclosed for inhibiting coke formation in pyrolytic reactors or furnaces during the pyrolysis operation. Rare earth elements or compounds thereof, such as cerium and lanthanum elements or compounds, are added to the particular hydrocarbonaceous medium undergoing such pyrolysis.

I claim: 
     
       1. A method of inhibiting the formation and deposition of pyrolytic coke on the heated metal surfaces of the structural and associated parts of a pyrolysis furnace which is being used to crack a petroleum feedstock to produce lower and/or olefinic hydrocarbon fractions, which method comprises adding to the feedstock a coke inhibiting amount of a rare earth element or rare earth containing compound. 
     
     
       2. A method as recited in claim 1 wherein said surfaces are heated, during said cracking, to a temperature of about 1400° F. or higher.   
     
     
       3. A method as recited in claim 2 wherein the feedstock is mixed with steam for enhancement of the cracking thereof. 
     
     
       4. A method as recited in claim 2 wherein said rare earth element or compound is added to said feedstock during cracking thereof. 
     
     
       5. A method as recited in claim 2 wherein said rare earth element or compound is added to said feedstock prior to cracking. 
     
     
       6. A method as recited in claim 2 wherein said rare earth element or compound is added to said feedstock in an amount of about 0.1-5000 parts of said rare earth per million parts of said feedstock. 
     
     
       7. A method as recited in claim 6 wherein said rare earth is added in an amount of about 5-1000 ppm per million parts of said feedstock. 
     
     
       8. A method as recited in claim 1 wherein said rare earth element or compound is chosen from the group consisting of rare earth elements, inorganic rare earth compounds and organic rare earth compounds. 
     
     
       9. A method as recited in claim 8 wherein said rare earth element or compound is elemental cerium, a cerium containing compound, elemental lanthanum, or a lanthanum containing compound. 
     
     
       10. A method as recited in claim 8 wherein said rare earth element or compound comprises elemental cerium or a cerium containing compound. 
     
     
       11. A method as recited in claim 8 wherein said rare earth element or compound comprises elemental lanthanum or a lanthanum containing compound. 
     
     
       12. A method as recited in claim 10 wherein said cerium containing compound is selected from the group consisting of cerous nitrate hexahydrate, cerium oxide, and ceric ammonium nitrate. 
     
     
       13. A method as recited in claim 11 wherein said lanthanum containing compound comprises lanthanum nitrate hexahydrate. 
     
     
       14. A method of inhibiting the formation and deposition of pyrolytic coke on the heated metal surfaces of the structural and associated parts of a pyrolysis furnace which is being used to crack a petroleum feedstock to produce lower and/or olefinic hydrocarbon fractions, wherein said metal surfaces are heated to a temperature of 1400° F. or higher, said method comprising adding to said feedstock a compound selected from the group consisting of cerous nitrate hexahydrate, cerium oxide, ceric ammonium nitrate and lanthanum nitrate hexahydrate, said compound being added in an amount necessary to provide from about 0.1-5,000 parts of said cerium or lanthanum in said feedstock, based upon one million parts of said feedstock. 
     
     
       15. A method of inhibiting the formation and deposition of pyrolytic coke on the heated metal surfaces of the structural and associated parts of a pyrolysis furnace which is being used to crack a petroleum feedstock to produce lower and/or olefinic hydrocarbon fractions, which method comprises adding to the feedstock a coke inhibiting amount of a rare earth element or rare earth containing compound, said feedstock comprising ethane, propane, butane, light naphtha, gas oils or mixtures thereof. 
     
     
       16. A method as recited in claim 15 wherein said feedstock comprises ethane, propane, or butane or mixtures thereof. 
     
     
       17. A method as recited in claim 15 wherein said rare earth element or compound is elemental cerium, a cerium containing compound, elemental lanthanum, or a lanthanum containing compound. 
     
     
       18. A method as recited in claim 15 wherein said rare earth element or compound comprises elemental cerium or a cerium containing compound. 
     
     
       19. A method as recited in claim 15 wherein said rare earth element or compound comprises elemental lanthanum or a lanthanum containing compound. 
     
     
       20. A method as recited in claim 18 wherein said cerium containing compound is selected from the group consisting of cerous nitrate hexahydrate, cerium oxide, and ceric ammonium nitrate. 
     
     
       21. A method as recited in claim 20 wherein said lanthanum containing compound comprises lanthanum nitrate hexahydrate.